One example of a lock device is illustrated in FIG. 3. FIG. 3 is a configuration diagram of a background lock device according.
A base 1 provided to any one of a door side (movable side) and a body side (stationary side) is formed with a groove 1a into which a striker provided to the other of the door side (movable side) and the body side (stationary side) is capable of entering.
A hook 7 is rotatably provided to one side of the base by a pin 5, while a pawl 11 is rotatably provided to the other side of the base by a pin 9, with a groove 1a being interposed between the hook 7 and the pawl 11.
The hook 7 is formed with a groove 7a into which the striker 3 enters. Further, an outer peripheral portion of the hook 7 is formed with a protrusion 7b. 
The hook 7 in the state illustrated in FIG. 3 is at a lock position at which the striker 3 is restricted from being released from the groove 7a. The state of the hook 7, which is rotated by approximately 45 degrees in a clockwise direction from the state illustrated in FIG. 3, is an unlock position at which the striker 3 enters into the groove 7a. 
A lateral portion of the pawl 11 facing the hook 7 is formed with a recess 11a with which the protrusion 7b of the hook 7 is to be engaged.
By a spring 13 having one end locked to the hook 7 and the other end locked to the pawl 11, the hook 7 is biased in an unlock-position direction (direction indicated by the arrow A in the drawing), and the pawl 11 is biased to a direction of the hook 7 (direction indicated by the arrow B in the drawing).
In addition, the pawl 11 is connected to a lock-release cable 15.
Now, the operation of the above-described configuration will be described.
The state of FIG. 3 in which the hook 7 is at the lock position is a state in which the protrusion 7b of the hook 7 is engaged with the recess 11a of the pawl 11 to restrict the hook 7 from rotating in the unlock direction and thus it is in a state in which the striker 3 cannot be released from the groove 7a of the hook 7 (lock state).
If the lock-release cable 15 is pulled against the biasing force of the spring 13, the pawl 11 is released from the hook 7, and then the engagement of the protrusion 7b of the hook 7, so that the recess 11a of the pawl 11 is released. Thus, the hook 7 rotates in the unlock-position direction by the biasing force of the spring 13, and the striker 3 becomes a state which can be released from the groove 7a of the hook 7 (unlock state).
In contrast, in the unlock state, if the inner wall of the groove 7a of the hook 7 is pushed by the striker 3, the hook 7 rotates in the lock-position direction against the biasing force of the spring 13. Then, the protrusion 7b of the hook 7 and the recess 11a of the pawl 11 are engaged with each other, and then the hook 7 is restricted from rotating in the unlock-position direction, so that the striker 3 becomes in the lock state in a state which is not released from the groove 7a of the hook 7 (e.g., see Patent Document 1).